Summary of events at St. Louis Demolition Landfill

The department's Solid Waste Management Program has been working with the City of St. Louis to properly close St. Louis Demolition Landfill and move the facility into post-closure status. The landfill was built before the current landfill design and operating requirements took effect, so it was grandfathered in and not required to monitor for methane gas. As part of the process of properly closing the landfill, the DNR required the city to prepare an investigation plan and install three gas-monitoring wells along the western perimeter of the facility.

On Oct. 5, 2009, methane was detected above 2.5 percent by volume in a monitoring well on the west property boundary of the St. Louis Demolition Landfill.  In response, the Solid Waste Management Program required the city to notify the fire department and all properties within 1,000 feet of the effected wells.  The City of St. Louis has notified homes and businesses and offered to install methane detectors for structures within the 1,000 foot area.  On Oct. 21, 2009, eight additional monitoring wells were installed and the city hosted a public meeting to answer questions about the landfill. 

Methane gas

Landfill gas is a natural byproduct of waste decomposition from waste placed in a landfill such as wood and paper.  The principal components of landfill gas are methane and carbon dioxide.  Methane can be flammable or explosive if it accumulates in an enclosed space within 5 to 15 percent by volume.  Therefore, the department regulates the concentration of methane at the property boundary of the landfill to a level that does not pose a flammability risk (2.5 percent by volume). 

The department and the City of St. Louis are encouraging residents and business owners to use caution and call 911 if they smell gas or the St. Louis Fire Department at 314-533-3406 if they have concerns with their methane detectors.

Future actions

Additional investigation by the city is needed to determine if the methane is spreading off-site. Based upon the findings of the site characterization and investigation, the city will then coordinate their actions to prevent methane generated at the landfill from migrating off-site. The department will continue to work with the city until the methane gas is reduced in the monitoring wells to below the regulatory limit. The city is also required to continue monitoring the wells and report the readings to the department on a weekly basis. The department will continue to post the methane monitoring data online as it is received.